(a) Field of the Invention
The present invention relates to a liquid crystal display (LCD) device having a front light unit as a light source. The present invention also relates to a structure of a new electroluminescent device.
(b) Description of the Related Art
Reflection type LCD devices are generally used in portable apparatus such as mobile telephones, personal data assistants, mobile computers and the like. The reflection type LCD device includes a front light unit as a light source and is described in Japanese Patent Laid-Open Publication Nos. 2000-29008, 2000-19330 and 11-326903. The conventional reflection type LCD device having a front light unit is described below, with reference to the configuration described in the Publication No. 2000-29008 as an example.
The conventional reflection type LCD device having a front light unit includes a LCD unit 120 and a front light unit 110, which are stacked together so that the front light unit 110 is disposed in front of the LCD unit 120, as shown in FIG. 1. The front light unit 110 includes a cold cathode tube or a linear array of light emitting diodes, and is positioned in the vicinity of the edge of a light guide plate (layer) 112. Moreover, in this particular example, the front surface of the light guide plate 112 far from the LCD unit 120 has an inclined and stepped configuration, and a protective member 113 is disposed on top of the inclined and stepped surface.
The operation of the conventional LCD device is as follows. The light emitted from the light source 111 penetrates through a side surface 112a of the light guide plate 112, and following a variation in the course thereof at the reflective surface 112b, is transmitted through a light exit surface 112c and irradiated onto the LCD unit 120. The light irradiated onto the LCD unit 120 passes sequentially through a polarizing plate 126, a phase plate 125, a transparent substrate 124 and a liquid crystal layer 123, and is then reflected by a plurality of reflective members 122. The reflected light passes through the same members in a reverse direction, and is transmitted from the LCD unit 120 to the font light unit 110.
The amount of light transmitted from the upper surface of the reflective members 122 of the LCD unit 120 is controlled by the alignment direction of the liquid crystal molecules of the LC layer 123. Consequently, by controlling the voltage applied to the liquid crystal layer 123 separately for each of the reflective members 122, any desired pattern can be displayed by the LCD device.
The light from the LCD unit 120 is transmitted through the front light unit 110 toward the front side of the LCD device and reaches a viewer (not shown in the figure). In the configuration shown in FIG. 1, damage to the reflective surface 112b is prevented by the protective member 113.
Referring to FIGS. 20A and 20B, there is shown a cellular phone including the conventional reflection type LCD device having a front light unit. The cellular phone includes a first housing member 150 and second housing member 160, which are coupled to form a housing. The housing receives therein a LCD device 131, surface-mounted electronic parts 132, switch 136, speaker etc., which are mounted on a printed circuit board 130. Other parts 134 such as a vibrator and connectors are mounted on a flexible printed circuit board 133 and connected to the parts on the printed circuit board 130. A protective cover 161 is attached on the second housing member 160, for protecting the LCD device 131 against mechanical impact, moisture and stain. The protective cover 161 is made of a plastic material such as polycarbonate having a thickness of 1 mm. It is desired that the LCD device 131, especially if used in the cellular phone, have a smaller thickness.
The conventional reflection type LCD devices which utilize front light units are constructed so that light emitted from a light source positioned in the vicinity of the edge of a light guide plate is transmitted through the light guide plate, changes the course at the surface of the light guide plate, and then irradiates the reflection type LCD unit. Design of the mechanism for extracting the light from the light guide plate (such as a surface with a stepped or prism shaped configuration) is important, although it is difficult to ensure a uniform brightness across the entire display area of the LCD device.
Furthermore, this type of mechanism for extracting light may also reflect and change the course of external light during a display operation in an ambient light condition wherein the front light unit is not used as a light source, and thus may cause a deterioration in the display performance. Moreover, if foreign matter such as dust or oil adheres to the surface of the light guide plate of the front light unit, then such soiled areas produce excessive scattering of the light, making a uniform brightness even more difficult. Furthermore, the light emitted from the light source also leaks out from the external side surface of the light guide plate outside the LCD device, thereby degrading the optical efficiency, or the efficiency of the light power.
Moreover, LCD devices are known which have a function for displaying information using only a portion of the display area (hereafter referred to as a xe2x80x9cpartial display functionxe2x80x9d), such as for time of day and communication status information on the display device of a mobile telephone. With the front light unit of the conventional LCD device, it is not possible to selectively irradiate a specified area of the display device.
An object of the present invention is to provide a low cost reflection type LCD device equipped with a front light unit, which is capable of efficiently and uniformly illuminating a LCD unit and does not significantly degrade the display performance even with foreign matter adhered thereto.
Another object of the present invention is to provide a low cost reflection type LCD device having a partial display function.
A further object of the present invention is to provide a method for manufacturing a LCD device including a front light unit and having a simple structure.
A further r object of the present invention is to provide a small-size light unit implemented by an organic EL device.
In a first aspect of the present invention, a liquid crystal display (LCD) device includes a LCD unit and a front light unit disposed at a front side of the LCD unit, the LCD unit having a plurality of light reflective members arranged in a matrix, the front light unit including a light emission area for emitting light toward the LC unit and a transparent area for passing light reflected from light reflective members of the LCD unit toward a front side of the front light unit.
In a second aspect of the present invention, a liquid crystal display (LCD) device includes a LCD unit and a front light unit disposed at a front side of the LCD unit, the LCD unit having a plurality of light reflective members arranged in a matrix, the front light unit including a transparent electrode, an electroluminescent layer and a non-transparent electrode consecutively arranged as viewed toward a front side of the front light unit.
In a third aspect of the present invention, an electroluminescence device includes a substrate and a multi-layered structure including a transparent electrode, an electroluminescent layer and a non-transparent electrode, which are consecutively formed on the substrate, wherein the non-transparent electrode has a patterned structure.
In a fourth aspect of the present invention, a method for manufacturing a liquid crystal display (LCD) device including the steps of forming a LCD unit having a plurality of reflective members arrayed in a matrix, forming a transparent electrode in front of the LCD unit, forming an electroluminescent (EL) layer on the transparent electrode, and forming a non-transparent electrode on the EL layer and having a specified pattern.
In a fifth aspect of the present invention, a method for manufacturing a liquid crystal display (LCD) device including the steps of forming a non-transparent electrode having a specific pattern on a transparent protective member, forming an electroluminescent (EL) layer on the non-transparent electrode, forming a transparent electrode on the EL layer, and forming a LCD unit at a rear side of the transparent electrode.
In accordance with the LCD devices of the present invention, and LCD devices manufactured by the methods of the present invention, the specified structures of the front light unit effectively function as front light units for the LCD units.
In accordance with the EL device of the present invention, the new structure of the EL device can be used for a variety of purposes such as a lighting unit.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.